This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This is a Phase 3, randomized, double-blind, placebo controlled, safety and efficacy study of pirfenidone in patients with IPF. Approximately 260 patients at approximately 55 centers will be randomly assigned, ratio of 1:1 to receive pirfenidone 2403 mg or placebo equivalent administered in divided doses three times per day-TID with food. The primary outcome variable will be the absolute change in percent predicted forced vital capacity-FVC from Baseline to Week 60. Patients will be randomized by geographic region. Any patient identified for the study must be off all prohibited medications at least 28 days before screening. Once patients complete the washout period, they may enter the screening period that may last up to 42 days. If eligible to participate, patients will receive study treatment, pirfenidone or placebo, from the time of randomization for 60 weeks. This will be followed by a 4 week follow-up period.